/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.galaxy.nebula.core.listeners;

import javax.servlet.ServletContext;
import javax.servlet.ServletContextAttributeEvent;
import javax.servlet.ServletContextAttributeListener;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;

/**
 * Example listener for context-related application events, which were
 * introduced in the 2.3 version of the Servlet API. This listener merely
 * documents the occurrence of such events in the application log associated
 * with our servlet context.
 * 
 * @author Craig R. McClanahan
 * @version $Id: ContextListener.java 939521 2010-04-30 00:16:33Z kkolinko $
 */

public final class ContextListener implements ServletContextAttributeListener,
		ServletContextListener {

	// ----------------------------------------------------- Instance Variables

	/**
	 * The servlet context with which we are associated.
	 */
	private ServletContext context = null;

	// --------------------------------------------------------- Public Methods

	/**
	 * Record the fact that a servlet context attribute was added.
	 * 
	 * @param event
	 *            The servlet context attribute event
	 */
	public void attributeAdded(ServletContextAttributeEvent event) {

		log("attributeAdded('" + event.getName() + "', '" + event.getValue()
				+ "')");

	}

	/**
	 * Record the fact that a servlet context attribute was removed.
	 * 
	 * @param event
	 *            The servlet context attribute event
	 */
	public void attributeRemoved(ServletContextAttributeEvent event) {

		log("attributeRemoved('" + event.getName() + "', '" + event.getValue()
				+ "')");

	}

	/**
	 * Record the fact that a servlet context attribute was replaced.
	 * 
	 * @param event
	 *            The servlet context attribute event
	 */
	public void attributeReplaced(ServletContextAttributeEvent event) {

		log("attributeReplaced('" + event.getName() + "', '" + event.getValue()
				+ "')");

	}

	/**
	 * Record the fact that this web application has been destroyed.
	 * 
	 * @param event
	 *            The servlet context event
	 */
	public void contextDestroyed(ServletContextEvent event) {

		log("contextDestroyed()");
		this.context = null;

	}

	/**
	 * Record the fact that this web application has been initialized.
	 * 
	 * @param event
	 *            The servlet context event
	 */
	public void contextInitialized(ServletContextEvent event) {

		this.context = event.getServletContext();
		log("contextInitialized()");

	}

	// -------------------------------------------------------- Private Methods

	/**
	 * Log a message to the servlet context application log.
	 * 
	 * @param message
	 *            Message to be logged
	 */
	private void log(String message) {

		if (context != null)
			context.log("ContextListener: " + message);
		else
			System.out.println("ContextListener: " + message);

	}

}
